Remote control of mining machines



Oct. 22, 1968 B. G. PlDGEON 3,407,002

REMOTE CONTROL OF MINING MACHINES Filed Jan. 6, 1967 L-- A ...m- B C SSI S52) HG2.

United States Patent O 3,407,002 REMOTE CONTROL OF MINING MACHINES Brian G. Pidgeon, Barton-under-Needwood, Burton-on- Trent, England, assignor to `Coal Industry (Patents) Limited, London, England, a company of Great Britainy Filed Jan. 6, 1967, Ser. No. 607,815 Claims priority, application Great Britain, Jan. 11, 1966, 1,268/ 66 4 Claims. (Cl. 299-1) ABSTRACT F THE DISCLOSURE A control system for remotely controlling a longwall mining machine by the use of high frequency signals capacitively coupled into a waveguide, includes several portable high frequency transmitters having distinctive transmitted wave characteristics, for example different carrier frequencies. The transmitters are used over different sections of the face, and a receiver is automatically set to respond to that transmitter appropriate to the particular section in which the machine is for the time being operative.

This invention relates to a control system for remotely controlling a longwall mining machine by the use of high frequency signals capacitively or inductively coupled into an insulated conductor serving as a waveguide.

In a proposed remote control system for a longwall mining machine, an operator carries a small portable transmitter energised by the usual cap lamp battery, the transmitted signal being passed to and dissipated from an aerial which is conveniently mounted in the body of the operators helmet or in the harness used for carrying the transmitter. A guide wire in the form of an insulated conductor extends the length of the coal face and providing the operator is within a given distance of the wire, the dissipated signal is capacitively coupled into the guide wire which propagates the signal in the desired direction. The end of the guide wire terminates at a receiver mounted together with the switch-gear controlling the machine, the signals being amplified and filtered at the receiver to perform the various control functions; for example, to stop and to vary the speed of the machine, and to adjust the machines cutting horizon.

Selection of the different control functions is achieved by modulation of the transmitted carrier wave. For example, the transmitter may operate on a carrier frequency of 480 kc./s., and the operator may be able to select any one of a given number of audio frequencies within a given range, of say 2.4 and 4.7 kilocycles, to modulate the carrier wave frequency, and thereby effect the desired control.

This known system is designed to give remote control by a single operator only and problems arise if it is desired to share the control between several operators stationed at different points along the mine face, since conflicting commands may be received simultaneously at the receiver. An object of the present invention is to overcome this disadvantage.

According to the present invention a control system for remotely controlling a longwall mining machine by the use of high frequency signals capacitively or inductively coupled into an insulated conductor serving as a waveguide, comprises a plurality of portable high frequency transmitters each intended for use at a different section of the path of travel of the machine, each transmitter having means for selecting one of several modulation frequencies to modulate the amplitude of the transmitted carrier wave and each having a` distinctive transmitted wave characteristic which differs from that of the other ice transmitters, a receiver connected to the insulated conductor and adapted to effect a desired control function in response to a given modulation frequency and switch means operable to set the receiver to respond at any given instance to signals of a distinctive wave characteristic corresponding to one only of the transmitters, said switch means being responsive to the position of the mining machine so that upon the machine entering a particular section, the switch means operate automaticallyl to set the receiver to respond only to the signals emitted by the transmitter appropriate to that section. The transmitters may each be operable at a different carrier frequency and the switch means may operateto set the receiver to respond at any given instance to one only of the carrier frequencies. Alternatively the transmitters may operate at the same carrier frequency, each having modulation frequencies differently coded by pulsed interruptions, and the switch means may operate to set the receiver to respond at any given instance only to those modulation frequencies having a given code of pulsed interruptions. The switch means may comprise a plurality of magnetic proximity switches which are spaced along the path of travel of the machine and which are arranged to be operated by a magnet carried on the machine, one of said proximity switches being located at each junction between two contiguous sections of the face.

A specific embodiment of the present invention, given by way of example only, will be hereinafter described with reference to the accompanying drawings, in which:

FIGURE 1 shows a schematic representation of a control system in accordance with the present invention, and

FIGURE 2, a circuit diagram of part of the system.

Referring to the dawings, the illustrated control means are operable to effect remote control of a longwall mining machine 10 which is hauled to-and-fro in well known manner along a face conveyor 11. Control of the machine 10 is shared between a number of operators each responsible for control over a given section of the path of travel of the machine. In the illustrated example the machines path is shown divided into three equal sections, namely A, B and C although it will be understood that a greater or lesser number of sections may be established in any given installation depending on the length of section considered appropriate and the overall length of the path of travel ofthe machine.

Each operator carries a portable high frequency, low power transmitting set 12a, b or c, of known construction comprising a low frequency oscillator 13a, b or c, a high-frequency oscillator 14a, b or c, an emplifier 15a, b or c and an aerial 16a, b or c. Each low frequency oscillator 13a, b, or c includes a number of push-buttons (not shown) which can be selectively depressed by the operator to switch into the circuit a capacitor (not shown) to determine in the low frequency oscillator 13a, b or c an audio modulation frequency of the high frequency oscillator 14a, b or c. A modulated wave so obtained is applied to the amplifier 15a, b or c, the output of which is connected to the aerial 16a, b or c. The signal dissipated by the aerial is, in known manner, capacitively coupled into an insulated conductor 17 extending along the length of the longwall face and constituting a waveguide. The conductor 17 terminates at the input to an amplifier 18, and the amplified signal is passed to a channel selector 19 which is set in a manner to be described to respond only to signals of a given carrier frequency correspon-ding to one of the transmitting sets 12a, b or c, each of the latter having a carrier frequency different from the other transmitting sets. Signals of the appropriate frequency are passed to a controller 20 which is adapted to effect a particular control function in response to a given modulation frequency, e.g., to stop or start machine 10.

Switching of the channel selector 19 so that the receiver responds to the carrier frequency appropriate "to the section in which the machine 10 is for the time being present, is effected by movement of the machine I() itself as it passes from one section of the face into another section, in a manner now to be described.

Mounted upon the face conveyor II, one at each junction between contiguous control sections, are a pair of spaced magnetic proximity switches SSI, SS2 which are operated by a magnet 21 fixed to the machine 10. Each proximity switch SSI, SS2 is of a bi-stable kind which is adjusted from one stable condition into another stable condition each time the magnet 21 moves into the immediate vicinity of the switch.

Referring now particularly to FIGURE 2, the switches SSI, SS2 are in circuit with three relays R1, R2 and R3 which when selectively energised switch in respectively tuned circuits TCI, TC2 and TC3. The latter are tuned so as to be responsive respectively to the carrier frequencies appropriate to the transmitting sets 12a, b and c. When the machine 10 is in section A of the face, the switches SSI, SS2 are in the condition shown in FIGURE 2 in which relay R1 only is placed in circuit by switch SSI with a D.C. power supply P. The relay contacts RICI and R2C2 associated with relay R1 and thus made to connect tuned circuit TCI to the amplifier 18. In this condition the receiver is only responsive to the carrier wave frequency transmitted by transmitting set 12a; i.e., that set corresponding to section A so that control can only be undertaken by the operator responsible for section A who can effect a desired control by selecting a given modulation frequency on the low frequency oscillator 13a. Any signals received from the other two transmitting sets 12b, c whilst tuned circuit TCI only is switched in, will be rejected by the tuned circuit TCI.

Upon the machine passing from section A into section B, proximity switch SSI is switched by the magnet into its other stable state to switch out tuned circuit TCI and energise relay R2 to place tuned circuit TC2 in circuit with the amplifier. The receiver is now set to respond only to signals of the carrier frequency transmitted by transmitting set 12b, i.e., that transmitter appropriate to section B of the face. Similarly upon the machine-passing into section C and switching proximity switch SS2 relay R2 is de-energised and relay R3 energised to connect tuned circuit TC3 in circuit with the amplifier 18, the receiver now being responsive only to signals arising from transmitting set 12C appropriate to section C of the face.

When the machine 10 is reversed and moved back along the face passing through sections C, B and A, i.e., in the reverse sequence to that described above, the proximity switches SS2 and SSI are switched in turn to their original states so that in section B the receiver is tuned to respond only to signals of the carrier frequency appropriate to transmitting set 12b, and in section A, to signals from transmitting set 12a.

As previously mentioned, the transmitting sets are themselves known per se, and in use of such equipment, it is usual to arrange for a master signal to be continuously transmitted to maintain control, absence of the master signal resulting in shut-down of the controlled machine. This feature provides a fail-safe system in that if say the insulated conductor 18 is fractured or an operator moves away a given distance from the conductor 13, the machine I is de-energised. It will be appreciated that if the transmitter sets 12a, b and c are designed in this manner then each time the machine control is transferred from one operator to the next in-line, the master signal will instantaneously be no longer present at the receiver and the machine will thus stop and have to be restarted again by the new operator. This may give rise to some inconvenience and therefore to overcome this disadvantage, it is preferable to introduce time-delays into the system so that instantaneously both tuned circuits are connected simultaneously to the amplier 18 during the changeover from one tuned circuit to another so that the master signal is not interrupted during the changeover period.

It will be understood that modifications may be introduced into the invention as described above; for example, instead of each transmitting set having a different carrier frequency, the carrier frequency may be the same and the different transmitters distinguished by modulation frequencies which are differently coded by pulsed interruptions, each transmitter having a different code. In this arrangement, the receiver will be switched to respond at any given instance to those modulation frequencies having a given pulsed code, i.e., to one of the transmitters only.

The magnetic proximity switches may be replaced by switch means responsive to a machine position transducer, eg., the teeth of a haulage sprocket forming part of the haulage for the machine, may be scanned by a sensing head the switch means being operated after passage of a given number of teeth (corresponding to a given movement of the machine along the face) past the head.

I claim:

1. A control system for remotely controlling a longwall mining machine by the use of high-frequency signals use at a different section of the path of travel of the machine and each having a distinctive transmitted wave characteristic which differs from that of the other transcapacitively or inductively coupled into an insulated conductor serving as a waveguide, comprising a portable high frequency transmitter having means for selecting one of several modulation frequencies to modulate the amplitude of the transmitted carrier wave, and a receiver connected to the insulated conductor and adapted to effect a desired control function in response to a given modulation frequency, wherein the improvement comprises a plurality of portable high frequency transmitters each intended for mitters, and switch means adapted to set the receiver to respond at any given instance to signals of a distinctive characteristic corresponding to one only of the transmitters, said switch means being further adapted to be responsive to the position of the mining machine whereby upon the machine entering a particular section, the said switch means operate to set the receiver to respond only to the signals emitted by the transmitter appropriate to that section.

2. A control system as claimed in claim 1, wherein the transmitters are each adapted to be operable at a different carrier frequency and the said switch means are adapted to set the receiver to respond at any given instance to one only of the carrier frequencies.

3. A control system as claimed in claim 1, wherein the transmitters are adapted to operate at the same carrier frequency and each has modulation frequencies differently coded by pulsed interruptions, the said switch means being adapted to set the receiver to respond at any given instance only to those modulation frequencies having a given code of pulsed interruptions.

4. A control system as claimed in claim I, wherein the switch means comprise a plurality of bistable magnetic proximity switches which are spaced along the path of travel of the machine and which are arranged to be triggered by a magnet carried on the machine, one of said proximity switches being located at each junction between two contiguous sections of the face.

References Cited UNITED STATES PATENTS 3,206,751 9/1965 Knight 180-77X 3,293,521 12/1966 Van Vroonhoven 299-1 X ERNEST R. PURSER, Primary Examiner. 

